Field of the Invention
The present invention relates to an image processing technique for developing photographed data, and more particularly to an image processing technique that makes it possible to reflect a dynamic range of photographed data on image data after development.
Description of the Related Art
Conventionally, in developing photographed data, so-called white balance adjustment is performed for adjusting color signals by taking into account characteristics of an image pickup apparatus that has acquired the photographed data and photographing conditions. Through the white balance adjustment, if an object has a gray color, an image of the object as a result of the development is output in which the gray color is formed by the color signals made uniform in level.
However, in a case where the color signals become different in saturation level after white balance adjustment, proper white balance adjustment cannot be performed, and so-called coloring is sometimes caused in a high-luminance area of the image.
To solve this problem, there has been proposed a method in which a clip level is set according to the level of a color signal R before or after white balance adjustment, and color signals G and B which have been subjected to white balance adjustment are clipped at the set clip level (see Japanese Patent Laid-Open Publication No. 2000-13808).
Further, there has been proposed a method in which whether or not each color signal is in a saturated state is determined after performing white balance adjustment, and a color signal determined to be saturated is corrected according to a level of the other color signal different from the color signal in the saturated state (see Japanese Patent Laid-Open Publication No. 2004-328564).
However, in the method described in Japanese Patent Laid-Open Publication No. 2000-13808, information on color signals exceeding the clip level is lost, so that it is impossible to express gradation of a high-luminance area in the result of the development.
Further, in the method described in Japanese Patent Laid-Open Publication No. 2004-328564, correction dependent on the color signal level is insufficient. More specifically, when gradation in which a color and a luminance gradually change is developed, tone jump sometimes occurs in which a color signal is largely changed at a boundary between a non-saturated state and a saturated state. As a result of correction performed using color signals different in saturation level, coloring remains in a high-luminance area.